Neuropeptides have been demonstrated to exert a variety of effects upon lymphoid cells. The focus of this proposal is to examine the direct effects of the neuropeptides, Substance P (SP), vasoactive intestinal peptide (VIP), and somatostatin on IgA and IgM responses by gut-associated lymphoreticular tissues (GALT). To address this question, well characterized B tumor cell lines and purified B-cell subpopulations from the GALT will be employed.To meet this objective, the following lines of investigation are proposed.First,the immunoregulatory effects of these neuropeptides on antibody secretion, surface antibody expression, and Class II MHC antigen expression on B-cells will be examined by isotype-specific ELISA and flow cytometry. Second, the B-cell differentiating capabilities of these neuropeptides will be assessedat the cellular and molecular levels (mRNA-cDNA hybridization). Third, the immunoregulatory effects these neuropeptides have in concert with B-cell stimulators (cytokine and/or antigen) on B-cells will be examined at both the cellular and molecular levels using procedures previously mentioned.Fourth, the contribution of these neuropeptides to mucosal immunity will be ascertained by blocking in vivo immune responses to sheep red blood cells (SRBC) by systemic and intraperitoneal administration of anti-neuropeptide monoclonal antibodies or by capsaicin treatment during neonatal life. B-cell immune responsiveness to SRBC will be assessed by direct plaque assay and by isotype-specific ELISPOT. Lastly, changes in B-cell neuropeptide and interleukin receptor levels asa consequence of neuropeptide stimulation will be examined by radiolabeled ligand binding studies of whole cells and by flow cytometry of B-cells stained with fluorochrome-conjugated monoclonal anti-receptor antibodies.